tipomac

I think it is pretty important to add that I have also replaced the cam chains between the intake and exhaust camshafts in both cylinder heads. I marked the corresponding sprocket teeth to the chains properly and when I did the replacement I was careful enough to match the markings.
After this the camshafts seemed to align up at TDC where the intake and exhaust camshafts factory marked sprockets point at each other.

tipomac

So the engine stalls and stall very fast as soon as the gas pedal is depressed. That means for some reason the engine doesn’t get enough fuel. I checked the fuel rail and the return line is completely dry. Is this normal? Also the incoming fuel supply line as soon as begin to open it it sputters fuel and trapped air out of the fuel rail. So there is pressure in the fuel rail but there are also trapped air bubbles in the rail. Is it possible that the fuel rail got somehow plugged with something along the long process?
Is it normal that the return line is completely dry? In the past anytime I opened the return line at the rail gasoline was flowing out the same way as it was flowing out from the fuel supply line and never any air. I know that there should be no air in the line by now after many ignition and many few seconds of smooth runs that eventually ended up in lean gasoline and also because of the trapped air bubbles in the rail some injectors did not receive gasoline but air from where they should get gasoline instead thus it slowly stalled the engine with some roughness in the stalling process.

Am I getting close to the root of the problem? Is it a plugged fuel rail or is there something wrong with the fuel pressure regulator?

tipomac

If it is the fuel pressure regulator this would explain the no fault codes. The trapped air bubbles in the fuel rail would explain why the car began to run for shorter and rougher after many trials as the temperature of the intake manifold increased the air bubbles have expanded because of the heat thus in created a more duel lean scenario fro the injectors.

Anybody who have more experience and/or knowledge about my cars present problem, please help me out. Thank you.

tipomac

I checked the fuel supply line if the pump pushes the fuel and it did so there seem to be no problem with the fuel pump. I also blew air into the fuel rail while the Fuel Pressure Regulator was taken off the rail. No problem. The fuel rail flows nicely. Next I attached the fuel supply line to the fuel rail again with F P Reg off the rail and turned the starter switch a few times so to filled up the fuel rail. Then I reattached everything including the Fuel Pressure Reg and the return line. After this the engine starts normally and runs normally then in a few seconds it stalled. Did a restart and again engine runs smooth then stalls a few seconds later. Another try and the engine again runs but stalls almost immediately. It seems it used up all the fuel in the rail.

So it seems the Fuel Pressure Regulator doesn’t open at all even after the fuel pressure builds up in the rail so eventually it plugs the fuel flow. Am I correct?

Do I need to replace the Fuel Pressure Regulator or the problem might be somewhere else?
Again there is no fault code of any kind after OBD2 scanning. Of course the FP reg is purely mechanical so there is no fault code scannable there at all, but there is no fault codes for anything else.

twentysevenlitres

You obviously have a fueling issue.
I cant answer whether a blocked fuel pressure regulator will create vapour lock. The whole system is self priming, but that relies on everything functioning correctly inculding the FP reg.
Its a cheap item, so if in doubt replace it.
Replace the fuel filter while your at it, as its also cheap and easy to do.

That leaves the fuel pump...
Perform a fuel flow test - disconnect the return line off the bottom the the FP reg, redirect it into a container and run 12V directly to the fuel pump for 15 secs.
Measure the result - from memory the pump should flow 700-800ml through the fuel pressure regulator (ie at pressure) in that time.
If it doesn't (and you've replaced the regulator and filter), look to the pump.

My experience with this was that the high pressure hose on the fuel pump assembly itself (from the actual pump to the high pressure fitting on the assembly) had a split which was preventing pressure build-up.
I also replaced the pump.

tipomac

Thank you Marty. It is an interesting problem since there was nothing problematic with the fueling system before the timing belt broke. However it took me close to 2 months to find a crank case flange for a good price ($60 instead of close to $500 at Audi dealer!) and also to find the good inlet valves 12 of them that I have found finally in England). During this time the fuel rail and the intake manifold was off the engine stored on the ground floor of the garage.

Is it possible that because of this long storing the Fuel Pressure regulator somehow gone bad maybe because it probably dried out? I am totally puzzled about this, especially after the tedious work I have done on the car with the valve jobs, cleaning the heads, replacing many things including the crank case flange …etc. how the heck now this fueling issue came about like a curse? Everything seems alright, timing is good, vacuum lines seems ok and now this fuel system issue. Well it would have been too nice had the car started and been running no problem after this so something needed to come up. At least I am happy for that I did my first timing belt job, first ever valve seatings, heads, crank case flange, water pump …etc. and these are seeming to be ok.

pocketchange

Verify the fuel filter is not the issue.. Please.

tipomac

So after thorough checking on everything at the fuel system. The pump generates correct pressure and the Fuel Pressure Regulator is also looks to be working fine. Although the Fuel Gage was indicating reserve level, but should have been enough there or at least I thought. However it wasn’t. As this banal thing caused the problem. Too low fuel level thus the pump could not pick up the fuel but only air and some fuel occasionally. I went to the Gas Station and back and poured about 4 liters into the tank and voila the engine started properly and kept on running. Timing seems to be fine. I did a test drive and everything seem to be fine. Car accelerates properly and there are no loud valve noises coming from any of the heads.
However I hear that there is a roller that squeaking. Most likely it is a timing belt roller or hopefully only a serpentine belt roller. If this squeaking doesn’t go away I have to look into this before another major failure occurs.
I am not really in the mood to redo the valve jobs all over again nor I want to redo the timing belt. It is not exactly a fun thing to do especially when it comes to ordering the parts that are not exactly cheap.

I hope this squeaking will eventually go away though. Wondering what it could exactly be?

Thank you for all the inputs so far!

twentysevenlitres

Yeah, complicated fuel pump arrangement on these!
The pump sits in a bowl that needs to be full of fuel in order for the pump to do its thing - part of the fuel is pumped back down into the tank to run a suction jet pump which sucks fuel back up to the bowl.
Under half a tank it is vital this suction pump does its thing, as the fuel pump is then above fuel level.

If the pump has a low fuel level in the bowl, it probably won't get enough fuel via the suction jet pump before running dry.
Dumping a few litres down the filler neck fills the bowl which will be enough to get the suction pump pumping.

Running correctly, these pumps can virtually run these tanks dry - not a bad set up really!